U.S. patent application number 11/040379 was filed with the patent office on 2005-07-21 for antimicrobial ceramic glaze.
This patent application is currently assigned to MICROBAN PRODUCTS COMPANY. Invention is credited to Olsson, Anders, Swofford, Howard Wayne.
Application Number | 20050158400 11/040379 |
Document ID | / |
Family ID | 34811344 |
Filed Date | 2005-07-21 |
United States Patent
Application |
20050158400 |
Kind Code |
A1 |
Olsson, Anders ; et
al. |
July 21, 2005 |
Antimicrobial ceramic glaze
Abstract
An antimicrobial ceramic glazing composition comprising zinc
borate for imparting antimicrobial characteristics to numerous
ceramic products. A method for producing the antimicrobial glazing
composition and ceramic products incorporating the antimicrobial
glazing composition.
Inventors: |
Olsson, Anders; (Satofta,
SE) ; Swofford, Howard Wayne; (Newton, NC) |
Correspondence
Address: |
KENNEDY COVINGTON LOBDELL & HICKMAN, LLP
214 N. TRYON STREET
HEARST TOWER, 47TH FLOOR
CHARLOTTE
NC
28202
US
|
Assignee: |
MICROBAN PRODUCTS COMPANY
Huntersville
NC
|
Family ID: |
34811344 |
Appl. No.: |
11/040379 |
Filed: |
January 21, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60538074 |
Jan 21, 2004 |
|
|
|
60567671 |
May 3, 2004 |
|
|
|
Current U.S.
Class: |
424/641 ;
501/49 |
Current CPC
Class: |
A01N 59/16 20130101;
C03C 8/04 20130101; C03C 2204/02 20130101; A01N 25/34 20130101;
A01N 59/16 20130101; A61K 33/32 20130101 |
Class at
Publication: |
424/641 ;
501/049 |
International
Class: |
A61K 033/32; C03C
003/14 |
Claims
What is claimed is:
1. An antimicrobial ceramic glazing composition comprising a
quantity of zinc borate sufficient to achieve a commercially
acceptable level of antimicrobial efficacy.
2. The antimicrobial ceramic glazing composition according to claim
1, wherein the antimicrobial ceramic glazing composition exhibits
at least a 98% relative reduction of bacteria after 24 hours when
tested in accordance with test method JIS Z 2801:2000.
3. The antimicrobial ceramic glazing composition according to claim
1, wherein the antimicrobial ceramic glazing composition has a
concentration of zinc borate of at least about 5,000 ppm.
4. The antimicrobial ceramic glazing composition according to claim
3, wherein the antimicrobial ceramic glazing composition has a
concentration of zinc borate of about 20,000 ppm to about 40,000
ppm.
5. The antimicrobial ceramic glazing composition according to claim
1, further comprising a quantity of zinc oxide.
6. The antimicrobial ceramic glazing composition according to claim
5, wherein the antimicrobial ceramic glazing composition has a
ratio of zinc borate to zinc oxide from about 10:90 to about
90:10.
7. The antimicrobial ceramic glazing composition according to claim
5, wherein the antimicrobial ceramic glazing composition has a
combined concentration of zinc borate and zinc oxide of at least
about 5,000 ppm.
8. The antimicrobial ceramic glazing composition according to claim
7, wherein the antimicrobial ceramic glazing composition has a
combined concentration of zinc borate and zinc oxide of about
20,000 ppm to about 40,000 ppm.
9. A ceramic article comprising the antimicrobial ceramic glazing
composition according to claim 1.
10. A ceramic article comprising the antimicrobial ceramic glazing
composition according to claim 5.
11. The ceramic article according to claim 9, wherein the ceramic
article is selected from the group consisting of toilets, bidets,
washbasins, towel rails, soap holders, toilet roll holders, water
control fixtures, and ceramic tiles.
12. The ceramic article according to claim 10, wherein the ceramic
article is selected from the group consisting of toilets, bidets,
washbasins, towel rails, soap holders, toilet roll holders, water
control fixtures, and ceramic tiles.
13. A ceramic article that exhibits antimicrobial properties, said
article comprising a ceramic substrate having at least one surface
and a glaze on a portion of said surface, said glaze comprising a
quantity of zinc borate sufficient to achieve a commercially
acceptable level of antimicrobial efficacy.
14. The ceramic article according to claim 13, wherein the ceramic
article exhibits at least a 98% relative reduction of bacteria
after 24 hours when tested in accordance with test method JIS Z
2801:2000.
15. The ceramic article according to claim 13, wherein the glaze
has a concentration of zinc borate of at least about 5,000 ppm.
16. The ceramic article according to claim 15, wherein the glaze
has a concentration of zinc borate of about 20,000 ppm to about
40,000 ppm.
17. The ceramic article according to claim 13, further comprising a
quantity of zinc oxide.
18. The ceramic article according to claim 17, wherein the glaze
has a ratio of zinc borate to zinc oxide of from about 10:90 to
about 90:10.
19. The ceramic article according to claim 17, wherein the glaze
has a combined concentration of zinc borate and zinc oxide of at
least about 5,000 ppm.
20. The ceramic article according to claim 19, wherein the glaze
has a combined concentration of zinc borate and zinc oxide of about
20,000 ppm to about 40,000 ppm.
21. The ceramic article according to claim 13, wherein the ceramic
article is selected from the group consisting of toilets, bidets,
washbasins, towel rails, soap holders, toilet roll holders, water
control fixtures, and ceramic tiles.
22. The ceramic article according to claim 17, wherein the ceramic
article is selected from the group consisting of toilets, bidets,
washbasins, towel rails, soap holders, toilet roll holders, water
control fixtures, and ceramic tiles.
23. A method for forming a ceramic glaze having built in
antimicrobial properties, the method comprising: preparing a
ceramic glazing composition, and adding to the ceramic glazing
composition a quantity of zinc borate sufficient to achieve a
commercially acceptable level of antimicrobial efficacy.
24. The method according to claim 23, wherein the ceramic glazing
composition has a concentration of zinc borate of at least about
5,000 ppm.
25. The method according to claim 24, wherein the ceramic glazing
composition has a concentration of zinc borate of about 20,000 ppm
to about 40,000 ppm.
26. The method according to claim 23, further comprising adding a
quantity of zinc oxide to the ceramic glazing composition.
27. The method according to claim 26, wherein the ceramic glazing
composition has a ratio of zinc borate to zinc oxide of from about
10:90 to about 90:10.
28. The method according to claim 26, wherein the ceramic glazing
composition has a combined concentration of zinc borate and zinc
oxide of at least about 5,000 ppm.
29. The method according to claim 28, wherein the ceramic glazing
composition has a combined concentration of zinc borate and zinc
oxide of about 20,000 ppm to about 40,000 ppm.
30. The method according to claim 23, further comprising coating a
substrate with the antimicrobial ceramic glazing composition.
31. The method according to claim 26, further comprising coating a
substrate with the antimicrobial ceramic glazing composition.
32. The method according the claim 30, further comprising firing
the coated substrate.
33. The method according the claim 31, further comprising firing
the coated substrate.
34. The method according to claim 32, wherein the fired coated
substrate exhibits at least a 98% relative reduction of bacteria
after 24 hours when tested in accordance with test method JIS Z
2801:2000.
35. The method according to claim 33, wherein the fired coated
substrate exhibits at least a 98% relative reduction of bacteria
after 24 hours when tested in accordance with test method JIS Z
2801:2000.
36. The method according to claim 32, wherein the fired coated
substrate is selected from the group consisting of toilets, bidets,
washbasins, towel rails, soap holders, toilet roll holders, water
control fixtures, and ceramic tiles.
37. The method according to claim 33, wherein the fired coated
substrate is selected from the group consisting of toilets, bidets,
washbasins, towel rails, soap holders, toilet roll holders, water
control fixtures, and ceramic tiles.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is entitled to the benefit of, and claims
priority to provisional U.S. Patent Application Ser. No.
60/538,074, filed on Jan. 21, 2004, and provisional U.S. Patent
Application Ser. No. 60/567,671, filed on May 3, 2004, each of
which is incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of antimicrobial
protection. More specifically, the present invention relates to a
composition for imparting built-in and long lasting antimicrobial
characteristics to ceramic products. In particular, the present
invention pertains to ceramic glazing compositions that impart
built-in antimicrobial characteristics to ceramic products.
BACKGROUND OF THE INVENTION
[0003] The field of providing products with built-in antimicrobial
protection has grown tremendously over the past several years. What
once started out as a premium or novel option for high-end consumer
products and medical devices has now grown into a mainstream
characteristic found in many consumer products. Consumers can go to
any home improvement center and see dozens if not hundreds of
products that claim some degree of resistance to microbiological
growth or contamination. Some major retailers have specific
sections devoted to such antimicrobial products.
[0004] Antibacterial products have been introduced into plastics,
textiles, liquids, metal coatings, and an array of other types of
materials. However, there remain several areas of consumer and
commercial products in which development of commercially viable
antimicrobial products has proven difficult. One such area is
ceramic coatings.
[0005] Ceramic coatings are commonly used in products that store,
treat, or transport water and liquid waste. Ceramic toilets,
urinals, bidets, bathroom basins, flooring tiles and other bathroom
fixtures are probably the most common example of such products.
[0006] Ceramic products used to collect and transport water are
often stained by scum and films of biologic origin (e.g., bacteria,
fungus, mold, mildew). To date, the primary method of removing
biological scum and film from these ceramic products has been to
abrade the ceramic surface in the presence of topical cleaning
agent. This process is time consuming and provides little or no
protection against future growth. Some cleaning agents can damage
the surface of the ceramic product. Therefore there is great
interest in the development of ceramic coatings that have built-in
protection against the growth and proliferation of microbes.
[0007] A few such built-in antimicrobial coatings are described in
the ceramic literature but they have not seen commercial success.
Existing technologies are somewhat limited. For example, the high
temperatures used in ceramic firing processes typically preclude
the use of organic antimicrobial agents. Inorganic silver-based
antibacterials are too expensive. Zinc oxide is known as having
antimicrobial characteristics and has been used in the preparation
of ceramic glazing compositions. However, known ceramic glazing
compositions that rely solely upon zinc oxide as an antimicrobial
agent have not shown antimicrobial efficacy sufficient for control
of microbial growth and proliferation on ceramic surfaces.
Accordingly, there is a need for a low-cost ceramic coating that
has built-in antimicrobial protection.
[0008] Thus, one object of the present invention is to provide a
new and useful antimicrobial ceramic coating that can impart
antimicrobial characteristics in a wide range of products.
[0009] A still further object of the invention is to provide this
ceramic coating at a cost that is acceptable to the marketplace.
Furthermore, this antimicrobial ceramic coating should be safe to
humans, exhibit commercially acceptable antimicrobial properties,
and most importantly, be compatible with existing ceramic
production processes.
[0010] These and other objects are achieved by the claimed
invention, which in one embodiment is an antimicrobial ceramic
glazing composition comprising a quantity of zinc borate sufficient
to achieve a commercially acceptable level of antimicrobial
efficacy. In preferred embodiments this ceramic glazing composition
also comprises a quantity of zinc oxide.
[0011] In a further embodiment, the invention is a ceramic article
that exhibits antimicrobial properties. The ceramic article
according to the invention has at least one surface and a glaze on
a portion of that surface. The glaze comprises a quantity of zinc
borate sufficient to achieve a commercially acceptable level of
antimicrobial efficacy. In preferred embodiments this ceramic
glazing composition also comprises a quantity of zinc oxide.
[0012] In yet another embodiment, the invention is a method of
making an antimicrobial ceramic glaze and a method of making a
ceramic article comprising the antimicrobial ceramic glaze.
DETAILED DESCRIPTION
[0013] As used herein, the terms "microbe" or "microbial" should be
interpreted to encompass any of the microscopic organisms commonly
studied by microbiologists. Such organisms include, but are not
limited to, bacteria and fungi as well as other single-celled
organisms such as mold, mildew and algae. Viral particles and other
infectious agents are also included in the term microbe.
[0014] For ease of discussion, this detailed description may make
reference to bacteria and antibacterial agents. This method of
presentation should not be interpreted as limiting the scope of the
invention in any way.
[0015] The claimed invention relates to ceramic coatings and in
particular to ceramic glazing on the outer surfaces of ceramic
products. The following brief discussion of vitreous china or
ceramic production is provided as an aid to the reader. This
discussion is presented in the context of the production of
bathroom fixtures. Those skilled in the art recognize that the
production process of other ceramic products may vary from that
which is presented below. The claimed invention, however, is
adaptable to any such variances.
[0016] The initial stage of a typical ceramic production process is
the production of barbotine or slip, a clay from which bathroom
ceramic products are made. Barbotine is made from a mixture of
clays, kaolin, phyllites, feldspar and quartz.
[0017] Individual pieces are cast by pouring the barbotine into
molds made of gypsum or microporous resin.
[0018] In the casting processes that use gypsum molds the parts are
formed by absorption of water contained in the barbotine through
the capillary action of the gypsum. As water leaves the barbotine
the part solidifies to a point where the mold can be opened. The
still malleable part is then removed from the mold.
[0019] Casting processes that use resin molds are called "high
pressure" processes. Parts are formed by filtering water contained
in the barbotine clay through micropores in the resin molds by the
application of pressure. The water is eliminated by injecting
compressed air along the molds.
[0020] Generally, gypsum molds are used for making parts with a
more complex geometry and that are produced in low volumes. Resin
molds are used for parts whose geometry is simpler and that are
produced in high volumes.
[0021] After casting and removal from the molds, the parts go for
drying in kilns under controlled humidity and temperature
(approximately 90.degree. C.). The drying cycle lasts about 7
hours, reducing the water content of the part from about 16% to
less than 1%. Following this, the parts are inspected to detect
possible flaws. The parts then go to the coating process. The
coating process is often referred to as the enameling step or the
glazing step.
[0022] The enameling step typically comprises the manual
application of ceramic enamel (also called ceramic glaze) on the
parts using guns in individual booths fitted with exhaust systems
and water curtains. Typical ceramic glaze is produced from a
mixture of kaolin, feldspar, quartz, colorings and other additives.
Once coated, the parts are fired in continuous kilns, reaching
temperatures of about 1,250.degree. C., in an approximately 15-hour
cycle. The firing process gives the glazed part the color and
transparent appearance that is typical of vitreous china
[0023] In one embodiment, the invention is a ceramic glazing
composition that provides commercially acceptable antimicrobial
efficacy after the firing process. In other words, the claimed
glazing reduces or substantially eliminates the growth and
proliferation of microbes on the surface of ceramic articles upon
removal from the firing process and without any further treatment
(e.g., further coating or painting of the ceramic part).
[0024] The antimicrobial ceramic glazing composition according to
the invention comprises components commonly utilized in the
preparation of ceramic glazing plus a quantity of zinc borate
sufficient to achieve a commercially acceptable level of
antimicrobial efficacy.
[0025] Zinc borate is the common term for a hydrated mineral-like
substance. Zinc Borate is most often used as a flame retardant and
smoke suppressant additive but it is sometimes used as an
antifungal agent. However, zinc borate is not known as an
antimicrobial agent in ceramic coatings.
[0026] The quantity of zinc borate required to achieve a
commercially acceptable level of antimicrobial efficacy for
finished ceramic products may vary depending upon the level of
contamination generally associated with the product. However, the
concentration of zinc borate for most commercial applications is at
least about 5,000 ppm of zinc borate. Concentrations above about
100,000 ppm can have adverse impacts on the aesthetic qualities of
the ceramic glaze. Concentrations of about 20,000 ppm to about
40,000 of zinc borate are preferred.
[0027] In an alternative embodiment, the glazing composition
according to the invention also comprises a quantity of free zinc
oxide. Free zinc oxide, as used herein, refers to an additional
amount of zinc oxide that is added to the glazing composition
separate from the zinc borate.
[0028] In the embodiments that employ a combination of zinc borate
and zinc oxide, the ratio of zinc borate to zinc oxide in the
glazing composition may range from about 90:10 to about 10:90. A
ratio of about 50:50 is preferred but may be altered depending upon
cost considerations. Preferably, a ratio of about 50:50 of zinc
borate to zinc oxide is added to the ceramic glazing composition at
about 2 weight % for the combination based upon the weight of the
ceramic glaze composition.
[0029] Similar to the embodiment that employs zinc borate, ceramic
glazing compositions comprising zinc borate and zinc oxide may have
at least about 5,000 ppm of a combination of zinc borate and zinc
oxide. Preferably, ceramic glazing compositions comprising a
combination of zinc borate and zinc oxide have about 20,000 ppm to
about 40,000 ppm of the combination. More preferably, about 20,000
ppm of the combination. Such concentrations, in varying ratios,
achieved greater than a 99% reduction of microbial species applied
to a ceramic surface coated with the claimed glazing composition.
Concentrations above 100,000 ppm may have adverse aesthetic effects
on the glazing.
[0030] If desired, other antimicrobial agents capable of surviving
the high temperatures of the enameling process may be added to the
glazing composition. Such agents include, but are not limited to,
silver (e.g., silver salts and silver zeolites), copper, and other
known metallic antimicrobial agents. Such agents can be added in
relatively minor amounts to supplement biocidal activity against
specific pathogens. Of course, such metallic antimicrobial agents
can be added in greater quantities if desired.
[0031] In a further embodiment, the invention encompasses a ceramic
article that exhibits antimicrobial properties. The claimed
antimicrobial ceramic article comprises a ceramic substrate having
at least one surface and a glaze on at least a portion of that
surface. The glaze utilized in this embodiment of the invention is
the same as that described in the first embodiment of the
invention. In other words, the glaze comprises a quantity of zinc
borate or a combination of zinc borate and zinc oxide that is
sufficient to achieve a commercially acceptable level of
antimicrobial efficacy.
[0032] In a preferred embodiment, the glazing will comprise at
least about 5,000 ppm of zinc borate. Concentrations above about
100,000 ppm of zinc borate may have adverse aesthetic effects on
the glazing. Concentrations of about 20,000 ppm to about 40,000 ppm
of zinc borate are preferred. Alternatively, the glaze comprises a
combination of zinc borate and zinc oxide, where the combined
concentration of zinc borate and zinc oxide is preferably at least
about 5,000 ppm Preferably, the combined concentration of zinc
borate and zinc oxide is in a range of about 20,000 ppm to about
40,000 ppm. If a combination of zinc oxide and zinc borate is used,
the ratio of zinc borate to zinc oxide may be about 90:10 to about
10:90, preferably about 50:50.
[0033] In a still further embodiment, the invention encompasses a
method of making an antimicrobial ceramic glaze and an article
having an antimicrobial ceramic glaze.
[0034] The antimicrobial ceramic glaze according to the invention
may be made by adding zinc borate or a combination of zinc borate
and zinc oxide, both of which are commercially available from a
number of sources, to an existing glazing composition. Those
skilled in the art of preparing glazing compositions will recognize
that the zinc borate and zinc oxide may be added separately or in
combination at any point in the process of making the glazing
composition.
[0035] Of course, care should be taken to ensure that the quantity
of zinc borate (or a combination of zinc borate and zinc oxide) is
sufficient to achieve a commercially acceptable level of
antimicrobial efficacy. In preferred embodiments the quantities of
these antimicrobial agents are the same as those set forth above in
the discussion of the glazing composition.
[0036] The method of making the claimed antimicrobial ceramic
article closely resembles the general method for making ceramic
articles set forth at the beginning of the detailed description.
However, in the method according to the invention, upon removal of
the article from the mold, the article is coated with the
antimicrobial ceramic glazing composition according to the
invention. The coated article is then fired as usual with the
ceramic coating retaining its antimicrobial characteristics even
after the firing.
EXAMPLES
[0037] Several ceramic articles were prepared to test the
antimicrobial characteristics of the recited glaze which comprises
a combination of zinc borate and zinc oxide. The test articles
comprised an underlying ceramic substrate made from a standard
commercial barbotine. The glaze used in the testing was a standard
glaze comprising silica sand, feldspar, calcium carbonate, china
clay, zirconium silicate, a small amount of CMC as a binder, and a
small amount of zinc oxide. To this basic glaze composition was
added varying quantities of zinc borate and zinc oxide. The glaze
composition according to the invention was applied to the articles
by spraying. The articles were then fired at 1200.degree. C. One
test article was prepared without any additional zinc oxide or zinc
borate for use as a control.
[0038] Six samples and one control were prepared in accordance with
the following table.
1 Antimicrobial Ratio of Zinc Borate Sample Concentration in the
Glaze to Zinc Oxide 1 20,000 ppm Zinc Borate:Zinc Oxide-90:10 2
40,000 ppm Zinc Borate:Zinc Oxide-90:10 3 20,000 ppm Zinc
Borate:Zinc Oxide-50:50 4 40,000 ppm Zinc Borate:Zinc Oxide-50:50 5
20,000 ppm Zinc Borate:Zinc Oxide-10:90 6 40,000 ppm Zinc
Borate:Zinc Oxide-10:90 7 (control) 0 ppm Standard Glaze which
includes some zinc oxide.
[0039] These six samples were tested in accordance with Japanese
Industrial Standard Z 2801:2000, one of the most common test
methods for antibacterial efficacy in inorganic ingredients. The
organism utilized in the test was E. coli, which is a pathogenic
microbe commonly found in human feces, and therefore also commonly
found on toilets and other bathroom products. Test results are
reported as a percent reduction of bacteria.
2 Bacteria on Bacteria on Relative Control Sample Reduction Sample
after 24 hours after 24 hours of Bacteria 1 5.4 .times. 10.sup.5
<1.0 .times. 10.sup.2 >99.98 2 5.4 .times. 10.sup.5 <1.0
.times. 10.sup.2 >99.98 3 5.4 .times. 10.sup.5 <1.0 .times.
10.sup.2 >99.98 4 5.4 .times. 10.sup.5 <1.0 .times. 10.sup.2
>99.98 5 5.4 .times. 10.sup.5 <1.0 .times. 10.sup.2 >99.98
6 5.4 .times. 10.sup.5 <1.0 .times. 10.sup.2 >99.98 7
(control) 5.4 .times. 10.sup.5 5.4 .times. 10.sup.5 0
[0040] The above results demonstrate that the glaze according to
the invention showed commercially acceptable efficacy against E.
coli relative to the control.
[0041] As noted previously, the ceramic glaze according to the
invention was designed to impart built-in antimicrobial protection
to a variety of ceramic articles. Accordingly, the scope of the
invention includes ceramic articles that incorporate the glazing
according to the invention. Such articles include, but are not
limited to, toilets, bidets, washbasins, towel rails, soap holders,
toilet roll holders, water control fixtures (e.g., hot and cold
water handles), ceramic tiles, and other ceramic applications.
* * * * *